U.S. patent number 8,608,800 [Application Number 13/247,840] was granted by the patent office on 2013-12-17 for switchable diffractive accommodating lens.
The grantee listed for this patent is Valdemar Portney. Invention is credited to Valdemar Portney.
United States Patent |
8,608,800 |
Portney |
December 17, 2013 |
Switchable diffractive accommodating lens
Abstract
A lens in accordance with the present invention includes an
accommodating cell having two chambers with at least one chamber
filled with optical fluid with the refractive index matching the
refractive index of the accommodating element separating them. The
accommodating element has a diffractive surface with surface relief
structure that maintains its period but changes its height due a
pressure difference between the chambers to redirect most of light
that passes through the lens between different foci of far and near
vision. The invention also includes a sensor cell that directly
interacts with the ciliary muscle contraction and relaxation to
create changes in pressure between the accommodating cell chambers
that results in changing surface relief structure height and the
lens accommodation.
Inventors: |
Portney; Valdemar (Newport
Coast, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Portney; Valdemar |
Newport Coast |
CA |
US |
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Family
ID: |
47627460 |
Appl.
No.: |
13/247,840 |
Filed: |
September 28, 2011 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130035760 A1 |
Feb 7, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61514413 |
Aug 2, 2011 |
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Current U.S.
Class: |
623/6.37;
623/6.31; 623/6.13; 351/159.11; 623/6.3 |
Current CPC
Class: |
G02C
7/085 (20130101); A61F 2/142 (20130101); A61F
2/1654 (20130101); A61F 2/1635 (20130101); G02C
7/04 (20130101); A61F 2250/0002 (20130101); G02C
2202/20 (20130101); A61F 2/14 (20130101) |
Current International
Class: |
A61F
2/16 (20060101) |
Field of
Search: |
;623/6.37,6.13,6.22,6.3,6.31
;351/159.04,159.18,159.61,159.11,159.15,159.35,159.44 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2011/092169 |
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Aug 2011 |
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WO |
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WO 2011/163668 |
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Dec 2011 |
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WO |
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Other References
Fujita T and Idesawa M, "Accommodation Assisted Glasses for
Presbyopia", Proceedings of the SPIE, 2002;4902:99-109 (Oct. 2002).
cited by applicant .
Kern SP, "Bifocal, electrically switched intraocular and eyeglass
molecular lenses" Proceedings of the SPIE, 1986;601:155-158 (May
1986). cited by applicant .
Li G, Mathine DL, Valley P, et al. "Switchable electro-optic
diffractive lens with high efficiency for ophthalmic application",
Proceedings of the National Academy of Science of the USA, 2006;
103: 6100-6104 (Apr. 2006). cited by applicant.
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Primary Examiner: Prebilic; Paul
Attorney, Agent or Firm: Hackler Daghighian &
Martino
Parent Case Text
This application claims priority from provisional application Ser.
No. 61/514,413 filed Aug. 2, 2011 and is to be incorporated in its
entirety.
Claims
What is claimed is:
1. An accommodating element for use in an ophthalmic device, said
accommodating element comprising: a formable element; and a
plurality of diffractive groove forming channels disposed on one
side of said formable element; a formable surface disposed on an
other side of said formable element comprising a variable
diffractive groove height in response to a change of pressure
differential between the plurality of channels on one side and the
formable surface on the other side, thereby changing the amount of
light directed to a non-zero order diffractive focus.
2. An ophthalmic device comprising: an accommodating element having
a formable surface on one side and a plurality of diffractive
groove forming channels disposed on the other side of said
accommodating element and in an operative relationship with the
formable surface for temporarily establishing the formable surface
with a non-zero relief structure having a variable height in
response to a change of pressure differential applied to the
formable surface on the one side and the plurality of diffractive
groove forming channels on the other side; and an optic combined
with said accommodating element, said optic being selected from a
group consisting of an intraocular lens, a corneal implant, a
spectacle lens, and a contact lens.
3. An ophthalmic device comprising: a membrane; a flexible
accommodating element disposed adjacent to said membrane for
creating an optically transparent chamber between said membrane and
one side of the flexible accommodating element; a plurality of
diffractive groove forming channels disposed in said one side of
the flexible accommodating element; a fluid disposed in said
optically transparent chamber between the flexible accommodating
element and the membrane within the plurality of diffractive groove
forming channels; a formable surface on an other side of the
flexible accommodating element configured to change shape in
relation to a change in a diffractive groove height of the
diffractive groove forming channel when subjected to a pressure
differential applied to the plurality of diffractive groove forming
channels on the one side and the formable surface on the other
side, said fluid having a refractive index matching a refractive
index of the flexible accommodating element; and an optic combined
with said accommodating cell, said optic being selected from a
group consisting of an intraocular lens, a corneal implant, a
spectacle lens, and a contact lens.
4. An ophthalmic device with a switchable diffractive surface,
comprising: a flexible element comprising a continuous surface on a
first side and a plurality of diffractive groove forming channels
on a second side opposite the first side, the plurality of
diffractive groove forming channels configured to change a
diffractive groove height of the continuous surface when subjected
to a pressure differential between the first side and second side
of the flexible element; a first optical fluid adjacent to the
continuous surface on the first side of the flexible element
comprising a non-matching refractive index in relation to the
flexible element; and a second optical fluid adjacent to and within
the plurality of diffractive groove forming channels on the second
side of the flexible element comprising a matching refractive index
in relation to the flexible element.
5. The ophthalmic device of claim 4, further including an first
optical membrane adjacent to the first optical fluid opposite the
first side of the flexible element forming an optically active
chamber between the first optical membrane and the flexible
element.
6. The ophthalmic device of claim 5, further including an second
optical membrane adjacent to the second optical fluid and abutting
the second side of the flexible element forming an optically
transparent chamber between the second optical membrane and the
plurality of diffractive groove forming channels.
Description
FIELD OF THE INVENTION
The present invention relates generally to a diffractive lens that
creates an image at different positions sequentially by the change
in magnitude of the surface relief structure height at its
diffractive surface, and more particularly to a diffractive
ophthalmic lens that changes surface relief structure height at one
of its surfaces to provide distance and near foci, and even more
particularly to diffractive accommodating lens that changes surface
relief structure height under the action of ciliary muscle.
BACKGROUND OF THE INVENTION
The diffractive lens of this disclosure can be applied outside or
within ophthalmic application. In later case the lens is called
ophthalmic lens. Ophthalmic lens in this disclosure is defined as a
lens suitable for placement outside the eye such as spectacles or
contact lenses or inside the eye such as aphakic and phakic
intraocular lenses placed in posterior or anterior eye chamber and
also included are less common vision correction lenses such as
artificial corneas and corneal implants.
For detailed explanation of the lens of this invention, the
application in the ophthalmology for Presbyopia correction and more
particularly to accommodating optic is used as a preferred
embodiment.
A fixed single power lens provides good quality vision but only
within a small range of viewing distances that is usually
significantly narrower than the range required from near to distant
vision. The resulted vision deficiency is called Presbyopia. There
is a significant effort to develop a lens for Presbyopia correction
in a form of multifocal refractive or diffractive type lenses that
provide multiple foci and also in a form of accommodating lenses
that may change their external surface shapes or positions inside
the eye for incremental power increase for near vision.
Accommodating ophthalmic lens described in this disclosure is a
lens that consequently changes the image positions between distance
and near foci by directing most of the available light to different
diffractive orders or between refractive state and one of the
diffractive orders under the action of ciliary muscle. It is
important to note that lens disclosed in this invention has
application outside accommodation and outside ophthalmic.
Natural accommodation as vision phenomenon is the ability of the
eye to focus at different distances. It involves the dioptric power
change of the eye provided by the crystalline lens shape change.
The accommodation is a multistage process and involves a number of
ocular elements: ciliary muscle, ciliary body, zonules, and lens
capsule and, at last, the crystalline lens itself, FIG. 1. It also
involves dynamically opposite actions of the corresponding ocular
elements such as ciliary muscle vs. zonules/capsular bag. For
instance, to accommodate for near vision, the ciliary muscle
contracts which moves the ciliary body inward towards the
crystalline lens, this relaxes the zonules attached to the ciliary
body which in turn, releases the elastic capsular bag to allow the
crystalline lens inside the capsular bag to take a more rounded
shape for higher optical power. For far vision, the ciliary muscle
relaxes which moves the ciliary body outward from the crystalline
lens; this creates tension on zonules which in turns stretches the
capsular bag that flattens the crystalline lens inside the
crystalline bag to reduce the optical power of the lens.
All the involved in accommodation ocular elements and especially
zonules and capsular bag vary with age and between different
individuals thus making an accommodating device that relies on the
action of zonules and crystalline bag to work as an extremely
challenging task.
It has been several efforts to develop ophthalmic lens that can
switch between optical conditions for far and near vision since
80th by using refractive optic. The principle of adjustment can be
divided into three types of approached: (1) deformable design that
changes lens shape in order to change its power, (2) translatable
design that changes lens position inside the eye in order to change
eye power and (3) refractive index adjustment design that changes
lens material refractive index in order to change its power. All
these designs were disclosed for the applications to the ocular
implants and spectacles; no application to contact lens has been
uncovered.
There are numerous US patents on and descriptions of deformable
designs (Fluid Vision, Flex Optic, NuLens, etc.) and translatable
designs (Synchrony, Crystalens, HumanOptics, TetraFlex, etc.) for
ocular implants where all of them utilize refractive optics.
Deformable design was also applied to spectacles, for instance
variable focus spectacle lens where the surface radius changes were
described by Fujita and Idesawa (Fujita T and Idesawa M,
"Accommodation Assisted Glasses for Presbyopia", Proceedings of the
SPIE, 2002; 4902:99-109). The interesting aspect of this paper is
the description of the gaze tracking for automatic lens power
adjustment for viewing object distance.
There are also few US patents on refractive index modification
designs. Nishimoto in U.S. Pat. No. 4,564,267 suggested a variable
focal lens using the Pockels effect by applying electric filed to
the electro-optic crystal to change material refractive index.
Similar idea was disclosed by Kern in the U.S. Pat. No. 4,601,545
using liquid crystal. Kern also proposed the application of his
invention to intra-ocular and spectacle lenses (Kern S P, "Bifocal,
electrically switched intraocular and eyeglass molecular lenses"
Proceedings of the SPIE, 1986; 601:155-158).
All the above disclosure was based on refractive optic for
accommodation application. Diffractive lens application to
accommodating implant was disclosed by Portney in US Patent
Application No: 20070032866 where the monofocal diffractive optical
surface changes its periods by bending in response to the
accommodating force from the ocular element of the eye thus
changing a separation between the diffractive orders and shifting
the diffraction image focus from one position to another.
Publication 20070032866 did not disclose a change in surface relief
height to switch light from one diffractive order to another. This
is to take full advantage of the diffractive optic to maintain
constant Add power as the separation between the diffraction orders
still relied on continuous change in focus position similar to a
refractive optic.
Diffractive optic offers advantages over refractive optic for
Presbyopia treatment where switching between far and near vision is
required instead of continuous change of optical power of
refractive optic where each power position is much more difficult
to control and where far vision, for instance, may be easily
varying even with a small change of accommodating force. More
detailed explanation of diffractive optic advantages is provided
below.
The advantage of the diffractive optic in switching between far and
near over the refractive optic was described in the application to
the spectacle lens by large group of researches: Li G, Mathine D L,
Valley P, et al. "Switchable electro-optic diffractive lens with
high efficiency for ophthalmic application", Proceedings of the
National Academy of Science of the USA, 2006; 103: 6100-6104. The
operation of the described spectacle lenses was based on electrical
control of the refractive index of thin layer of pneumatic liquid
crystal. Though the approach is feasible, it is very complicated
and expensive to execute and it also requires elective field
control for its operation which is problematic for ocular implants
and contact lenses. Haddock at el. in US Patent Application
20090256977 introduced further improvements to the above
diffractive lens manufacturability. The spectacle lenses under the
above design were released by PixelOptics under Em Power trade
name.
The described above systems used the electro-optical switching
between diffractive states for far and near vision by refractive
index modulation. The present invention utilizes mechanical optical
switching between far and near vision by changing the height of the
surface relief structure of the diffractive optic.
The present disclosure also describes the diffractive optic with
progressively changing foci by adjusting the periods of the
diffractive grooves. This can be applied not only to the surface
relief periodic structure of static single focus and multifocal
diffractive lens where the light split is constant and also to
dynamic diffractive lens where light is redirected between
different diffractive orders by mechanical or electro-optical means
of refractive index or surface relief modulations.
Iyer et al. in the US Patent Application 20110176103 referenced to
refractive-diffractive insert that provided progressive power
variation by optical communication between refractive and
diffractive regions. No reference to a diffractive optic that on
its own provides progressive foci by adjusting the periods of the
diffractive grooves was disclosure in Iyer's US Application.
Diffraction principle of image formation is utilized for the
disclosed accommodating ophthalmic lens. A diffractive lens
consists of a periodic structure responsible for the separation
between produced diffractive orders and is characterized by its
phase function analogous to a refractive lens description by its
surface sag equation. There two ways to change phase delay in the
diffractive structure of a diffractive optical element and switch
or redirect light between different foci, either by refractive
index modulation or by surface shape (relief) modulation.
Therefore, there are two types of diffractive structures: (1)
refractive index modulation structure and (2) surface relief
structure. First approach has been applied to spectacles as
referenced above publication by Li and his colleagues. For the
purpose of referencing in this disclosure, the first approach to
switch or redirect light between different foci by refractive index
modulation is called diffractive accommodating lens by refractive
index modulation and the second approach to switch or redirect
light between different foci by surface relief modulation is called
diffractive accommodating by surface relief modulation.
The proposed invention is based on the modulation of the surface
relief structure by maintaining its period and, therefore,
separation between diffractive order and changing its height in
order to control light distribution between the diffractive orders.
In the other diffractive structure that relies on the refractive
index modulation, the maximum thickness of the material within
which the refractive index changes is analogous to the higher of
the surface relief structure as explained above. For the purpose to
simplify a description of the refractive modulation structure, the
maximum thickness of the material within which the refractive index
changes is defined as the "refractive index amplitude" in this
embodiment.
The disclosed invention is applicable not only to spectacles lens
but contact lenses and ocular implants. Thus, the surface relief
structure of this invention maintains the same period but otherwise
changes its height in order to provide accommodation between far
and near vision.
A surface relief structure of diffractive surface can be formed by
different types of zone or groove shapes (sine, rectangular, for
instance) and a blaze shape shown on the FIG. 2 being the most
common one. A specific periodic blaze shape is cut into a
refractive surface which becomes the base surface of the
diffractive surface and the resulted lens becomes a diffractive
lens.
This disclosure will use blaze grating as an example but the
present invention is applied to any type of surface relief
diffractive surface that produces distance and near foci or, more
generally, at least two images at its diffractive orders by
shifting 100% or substantial portion (about 30% or more) of light
to different diffraction orders or refractive image position and a
position defined by one of the diffraction orders.
The distances from the diffractive surface to the foci created by
the diffraction orders can be quantified in terms of diffraction
powers associated with the diffraction orders similarly to a
refractive lens power definition. Zero-order diffractive power of
the diffractive surface coincides with the refractive power of the
refractive surfaces formed by the base surface of the diffractive
surface.
By the law of formation of a diffraction order, light can only be
channeled along the diffraction orders of the diffractive lens
where constructive interference can take place. It leads to the
discrete foci of a diffractive lens. Discrete nature of image
formation by a diffractive optic is the key characteristic utilized
by the diffractive accommodating lens of this invention.
Importantly, the image is physically formed at a given foci of the
diffraction order if a measurable percent of total light is
actually channeled along a given diffraction order. This depends
upon the light phase shift introduced by each blaze zone, i.e.
groove height or blaze material thickness (h), FIG. 2. The
construction of accommodating cell of the diffractive accommodating
lens of this invention is to control the change of the blaze
material thickness in order to channel 100% of light or most of the
available light consequently between two diffractive orders or a
diffractive order and refractive state where the grooves height is
zero. These two image positions associate with far and near
foci.
Geometry of the diffraction grooves is easier to explain by the
"geometrical model" of the grating: 100% efficiency (light
transmittance) in m-order can be achieved if the direction of the
imaginable blaze ray defined by the refraction at the blaze
coincides with the direction of m-order diffraction, (Carmifia
Londofio and Peter P. Clack, Modeling diffraction efficiency
effects when designing hybrid diffractive lens systems, Appl. Opt.
31, 2248-2252 (1992)). It simply means that the blaze material
thickness is designed to direct the blaze ray along the m-order
diffraction produced by the blaze groove widths for the design
wavelength of light.
In a simple paraxial form the circular grating zones, also called
grooves, echelettes or surface-relieve profile, can be expressed by
the formula r.sub.j.sup.2=jm.lamda.f, i.e. the focal length of
m-order diffraction (m=.+-.1, .+-.2, etc.) for the design
wavelength (.lamda.) can be closely approximated by the following
formula:
.times..times..times..times..lamda. ##EQU00001##
This is the formula typically used for the groove widths
calculation in diffractive optic that produces wavefront close to a
spherical shape, i.e. small amount of aberration. The locations of
groove's borders are simply determined analytically by radii
r.sub.j. The radii per Equation 1 define diffractive lens periodic
structure which, in this case, produces spherical wavefront that
defines single focal length (f.sub.m) for diffractive order (m). In
general, the periodic structure can be surface relief structure
where surface shape manifests the periodic structure per Equation 1
or close to it to produce quasi-spherical wavefront, or refractive
index modulation structure where the material variation of the
diffractive lens manifests refractive index periodic structure per
Equation 1.
In case of the surface relief structure, and in the paraxial
approximation the blaze material thickness to produce 100%
efficiency at m-order is
.times..times..lamda.' ##EQU00002## where n=refractive index of the
lens material and where m=refractive index of the surrounding
medium.
A surface relief may be formed by different shapes of the periodic
diffractive structure and not only by a blaze shape and for the
generality of the present invention the term "groove" is used as
the description of the variety of shapes of the diffractive
structure including multi-order phase grating (MOD) which is useful
in reducing dispersion or chromatic aberration of the diffractive
optical element.
Phase function defines diffractive optic analogous to sag equation
defining refractive optic. A phase function is usually defines in
polynomial form as shown by the equation 3 below, The examples of
the phase functions in terms of polynomial phase coefficients is
provided in the Table 3 for diffractive optic with small and large
spherical aberrations.
In case of small aberration, the periodic structure of the
diffractive optic is quite accurately defined by the equation 1 for
given focal distance. In case of significant spherical aberration
of the diffractive lens to be introduced in order to extend the
range of vision around one of the focus of the diffractive order,
the calculation of the groove shapes can be conducted numerically
similar to the method described by Portney in the US Patent Appl.
No: 20100066973 for multifocal diffractive lens: a) calculating
diffractive structure phase coefficients that produce diffractive
focus of a selected accommodating state. Usually (-1)-order
diffraction is allocated to near focus.
.PHI..function..times..pi..lamda..function..times..times..times.
##EQU00003## Formula (3) is (-1)-order (near focus) phase function
with phase coefficients a.sub.i calculated over the contribution of
the eye optical system. b) numerically calculating a 100%
diffraction efficiency groove shape and height h(r.sub.i) that
produces the defined phase coefficients and the groove widths
defining by the phase function modulo 2.pi.p cycle where p=1, 2, .
. . .
The objective of the present invention is to provide a diffractive
accommodating lens that offers a sequential change in the optical
states with substantial portion of the available light switched or
redirected between two images for far or near vision under the
action of the ciliary muscle contraction and relaxation. The lens
that forms images at two image positions with image at one image
position is formed by non-zero order diffraction and image at
another image position is fainted by either a different order
diffraction or refraction is disclosed by this invention.
The invention offers also an option to bypass the ocular elements
such as zonules and capsular bag which reduce a reliability of an
accommodating lens and rely on the direct interaction with the
ciliary muscle. This is accomplished due to the ability to the
diffractive accommodating lens of this invention to switch foci
between far and near vision by only a small amount of the material
transfer which can be accomplished by the ciliary muscle action. A
volume of the material transfer involved in the diffractive
accommodating lens of this invention is only in a small fraction of
milliliter.
A material transfer in accommodating optic may occur directly from
a sensor cell implanted or installed next to ciliary muscle in
order to respond to their relaxation and contraction. This is
accomplished in ocular implants such as aphakic, phakic including
corneal implants. A material transfer may occur indirectly from a
sensor cell by the cell transferring electronic signal to an
external visual aid such spectacles, for instance, to control its
optical states between far and vision. Ultimately, electronic
transfer signal can be conducted between sensor cell and implants
with optical state change per these inventions by mechanical or
electronic means.
As a minimum, the lens of the present invention may still rely on
the interaction with the capsular bag or vitreous as indirect means
to respond to ciliary muscle actions during accommodation.
The invention disclosures different option for optical enhancement
of the range of vision at image formed at the diffraction order on
the example of extending the range towards intermediate vision from
the near vision formed by (-1)-order diffraction.
In the present invention the periodic structure of the diffractive
surface is maintained between the optical states of far and near
vision but the phase delay changes between when switching between
these optical states. The invention disclosure describes surface
relief diffractive lens that switches optical states of far and
near vision by changing phase delay with surface relief height.
Certain invention disclosures related to multi-zonal use of the
diffractive surface the zones have different periodic structure to
provide different foci for the same diffractive order is applicable
to general phase delay wither by the height of the surface relief
or refractive index modulation.
Additional invention disclosure describes periodic structure change
to increase spherical aberration and associated with it depth of
focus around focus position produced by non-zero diffractive order
as compared with diffractive lens with small amount of spherical
aberration. This disclosure is applicable to static diffractive
multifocal lens where light split is constant as well as to dynamic
diffractive accommodating lens where light split between far and
near vision changes.
The invented lens can be applied outside the eye in a form of
spectacles, contact lens or even in non-ophthalmic applications
required the image position change without moving the lens
itself.
SUMMARY OF THE INVENTION
A lens in accordance with the present invention consists of front
and back surfaces and accommodating cell situated between them. In
a particular embodiment, the accommodating cell consists of two
chambers with at least one chamber filled with optical fluid with
the refractive index matching the refractive index of the
accommodating element separating the chambers. The accommodating
element is having the surface relief structure that maintains its
period but changes its height due the pressure difference between
the chambers. The accommodating cell may include another chamber
connected with the external to the lens medium (aqueous humour,
air, stroma, tear layer). The accommodating cell may also have
chambers both filled with optical fluids of different refractive
indices. The accommodating element shape change creates different
diffractive groove heights to redirect most of light that passes
through the lens image forming zone between different image
positions of far vision and near vision foci. The add power for
near vision is defined by the periodicity of the surface relief
structure. Thus, the accommodating element includes formable
surface with a plurality of sub-elements disposed on it for
temporarily establishing a surface zone with a non-zero relief
structure height upon change of pressure on this formable surface.
For instance, one focus can be refractive formed by the refractive
surface with surface relief surface with zero heights and another
focus is formed by the diffractive surface relief of specific
non-zero height to direct most the available light that passes
through the lens image forming zone along the corresponding to this
height non-zero order diffraction. Another option is to have the
one surface relief non-zero height to pass most of light along the
corresponding to this height non-zero order diffraction and then to
change the s height magnitude to direct most of the available light
passing through the lens image forming zone to another
corresponding to this height non-zero order diffraction.
This invention describes the device called diffractive
accommodating lens or DAL which can overcome the complexity and
individual dependence of the forces involved in eye accommodation.
The disclosure involves two aspects of the invention: (1) The
diffractive accommodating system that includes Sensor Cell and DAL
interacts directly with the ciliary muscle in changing its focus
state. It is well known that the ciliary muscle operation is
maintained for different age thus proving a reliable action for the
accommodating device. All other ocular elements involved in the
accommodation such as zolules, capsular bag and the crystalline
lens itself are highly age and individual condition dependent and
can't be relied on for consistent operation of accommodating
devices. The invention discloses Sensor Cell that is placed at the
location of the Scleral Spur to interact directly with ciliary
muscle and transfer the pressure change to the Diffractive
Accommodating Lens to change its states between far and near
vision. A diffractive accommodating lens DAL according to this
invention may also rely on the secondary accommodating effect where
ciliary muscle contraction effects the choroid tension that
increases vitreous pressure that causes crystalline lens-zonule
complex to move forward. In this case, the crystalline lens is
replaced by the DAL and the vitreous pressure change switches the
states of the DAL between far and near vision. (2) The diffractive
accommodating lens DAL provides two states of accommodation for far
and near vision thus maintaining each state only temporary.
Technically it means that the device acts in digital binary sense
and does not change its accommodation effect if a force exerted by
ciliary muscle does not exceed certain threshold level. This allows
maintaining stability of the vision in relaxed state even under
some fluctuation of the forces. Thus, the operation of DAL relies
only on a single parameter such as a force threshold between
relaxed and contracted states of the ciliary muscle of a given
individual which can be even adjusted in vivo.
A diffractive lens that directs 100% or most of the available light
that passes through its image forming zone to (-1)-order
diffraction is called kinoform and the corresponding diffractive
lens acts as one of the states of the diffractive accommodating
lens DAL of this disclosure, specifically for near focus. A
diffractive lens that directs 100% of most of the available light
to (+1)-order diffraction may also act as one of the states of the
diffractive accommodating lens DAL of this disclosure, specifically
for far focus.
Multifocal diffractive lens is also used to provide two image
positions for far and near vision for Presbyopia treatment but the
issue with this type of design is that in-focus image at each image
position includes out-of-focus image resulted in blur that reduces
each image contrast and contributing to halo and glare perception.
One way to quantify multifocal diffractive lens imaging is to state
that total amount of light used to form in-focus images at certain
aperture size is less than total amount of the available light
entering the lens within the same aperture size. The reason is that
the light is split between in-focus images at two image positions
to form both in-focus images simultaneously.
In case of diffractive accommodating lens of this invention, light
utilizes much more efficiently, the total amount of light used to
form in-focus images at certain aperture size exceeds the total
amount of light entering the lens within the same aperture size.
The reason is that both in-focus images form sequentially by
redirecting some light from in-focus image at one image position to
in-focus image at another image position. It is possible that the
diffractive accommodating lens of this also invention also split
light between the images at two image positions simultaneously but
the use of light for in-focus image is higher than in multifocal
diffractive lens because the some or all amount of light is
redirected inform in-focus image at one image position to the
in-focus image in another image position. This improves image
contrast and reduces halo and glare as compared with multifocal
diffractive optic.
The preferred embodiment creates the change between the optical
states of the acting surface by changing pressure between the
chambers located at both sides from the surface but, in general,
the surface shape change from one diffractive order to another or
to refractive state for directing most of the light to one or
another image positions can be accomplished by other means
including mechanical transducers or electrical or magnetic
force.
The present disclosure also describes the diffractive optic with
progressively changing foci by adjusting the periods of the
diffractive grooves. This can be applied not only to the surface
relief periodic structure of static single focus and multifocal
diffractive lens where the light split is constant and also to
dynamic diffractive lens where with light is redirected between
different diffractive orders by electro-optical or mechanical means
by refractive index or surface relief modulations. The mechanical
means of surface relief modulation to provide dynamic switch
between far and near vision is provided in this invention
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages and features of the present invention will be better
understood by the following description when considered in
conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a portion of eye anatomy related to the
accommodation process. The ciliary body of the eye has three basic
functions: aqueous production and removal, accommodation, and the
formation of vitreous mucopolysaccharide. The ciliary muscle
initiates the accommodation process and situates inside the ciliary
body.
FIG. 2 illustrates a prior art diffractive lens with blazed
periodic structure forming different diffraction orders along which
the light can only be channeled. It illustrates the optical
principle used by the accommodating cell of this invention for
switching between far and near vision. The FIG. 2 also illustrates
a "geometrical model" of the diffractive lens through the
relationship between the imaginary blaze ray defined by the
refraction at the blaze and directions of the diffraction
orders.
FIG. 3 shows a simplest form of the accommodating cell
configuration as a rectangular disc of about 4-6 mm diameter and
about 0.1-0.3 mm thickness. The minimum diameter of the
accommodating is around 3 mm and may reach about 6 mm diameter. The
thickness can be as small as about 0.1 mm. The accommodating cell
is situated inside the lens or it may take the shape of the lens
itself by including required surface curvatures by its external
surfaces instead of flat surfaces shown in the FIG. 3.
FIG. 4 demonstrates a cross-section of a preferred embodiment of an
accommodating cell in a relaxed state. The accommodating cell of
this embodiment includes two chambers filled with optical fluids,
silicone fluid, for instance, separated by the membrane called
accommodating element that has the ability to change its surface
shape with a difference in pressure between the chambers. One
chamber is filled with optical fluid of matching refractive index
as the material of the accommodating element separating the
chambers to make the light passing between the material separating
the chambers and the optical fluid undisturbed by the surface shape
facing this chamber. This is optically transparent chamber or OTC.
Optical fluid of non-matching refractive index fills the other
chamber. Thus, a light refraction takes place only at the surface
facing this chamber. This is optically active chamber or OAC. The
FIG. 4 demonstrates that the surface facing the chamber filled by
optical fluid of non-matching refractive index (OAC) is smooth
refractive surface type for Far vision in relaxed state as one of
the examples of surface configuration.
FIG. 5 demonstrates a cross-section of the accommodating cell,
shown in FIG. 4, in a stressed state. The accommodating element
between the chambers takes a shape of diffractive surface
manifested by the diffractive grooves facing the chamber filled
with optical fluid of non-matching with the accommodating element
material refractive index (OAC). The maximum diffractive grooves
heights (blaze material thickness) is restricted by the geometry of
the accommodating element and the thickness of the chamber filled
with optical fluid of matching refractive index (OTC), i.e. most of
the available light passing the image forming optical zone of the
diffractive accommodating lens is directed to (-1)-order
diffraction by the created diffractive surface of the accommodating
element.
FIG. 6 demonstrates a cross-section of a preferred embodiment of an
accommodating cell in a relaxed state. The accommodating cell of
this embodiment includes two chambers the first one is filled with
optical fluids, silicone fluid, for instance, and the second
chamber is connected with the external medium surrounding the
ophthalmic lens (aqueous humour in case of intraocular lens, stroma
or air in case of corneal implant, tear layer or air in case of
contact lens and air in case of spectacle lens). The chambers are
separated by the membrane called accommodating element that has the
ability to change its surface shape with a difference in pressure
between the chambers. First chamber is filled with optical fluid of
matching refractive index as the material of the accommodating
element separating the chambers to make the light passing between
the material separating the chambers and the optical fluid
undisturbed by the surface shape facing this chamber. This is
optically transparent chamber or OTC. Thus, a light refraction
takes place only at the surface facing the chamber. The second
chamber is optically active chamber or OAC. The FIG. 6 demonstrates
that the surface facing the second chamber is smooth refractive
surface type for Far vision in relaxed state as one of the examples
of surface configuration.
FIG. 7 demonstrates a cross-section of the accommodating cell,
shown in FIG. 6, in a stressed state. The accommodating element
between the chambers takes a shape of diffractive surface
manifested by the diffractive grooves facing the second chamber
connected to the external medium of the ophthalmic lens. The
maximum diffractive grooves heights (blaze material thickness) is
restricted by the geometry of the accommodating element and the
thickness of the second connected with external medium, i.e. most
of the available light passing the image forming optical zone of
the diffractive accommodating lens is directed to (-1)-order
diffraction by the created diffractive surface of the accommodating
element.
FIG. 8 demonstrates an assembly of the accommodating cell
consisting of three elements: front and back membranes to form
external walls of the corresponding chambers filled with optical
fluids and accommodating element forming the wall between the
chambers. The membrane is shown as flat surfaces but can be curved
to provide refractive powers. The construction of the accommodating
element can be made with diffractive surface of 1-order diffraction
for far vision and refractive surface for near vision or even as
switching between surface reliefs of different heights to redirect
light to the corresponding different orders diffraction.
FIG. 9 illustrate front view of one of the embodiments of
intraocular lens consisting of lens optic, haptics or supporting
elements and addition of the connecting flexible element attached
to the accommodating element situated inside the intraocular lens
of this embodiment. The connecting element is to connect the
accommodating element with the sensor cell that interacts with the
ciliary muscle to transfer the force from the ciliary muscle
contraction and relaxation into a difference in pressure between
the chambers of the accommodating cell.
FIG. 10 shows the cross-section of the intraocular lens of FIG. 7.
It demonstrates the accommodating cell situated inside the
intraocular lens with connecting element attached to it at one end
and the other end attached to the opposite edge of the intraocular
lens optic for its temporary fixation during the lens implantation
inside the eye. This end of the connecting element is separated
from the intraocular lens after the implantation connection to the
sensor cell.
FIG. 11 illustrates the assembly of the intraocular lens shown on
the FIGS. 7 and 8. The intraocular lens assembly of this particular
embodiment consists of three elements: front element which can be
attached to the back element by the front wedge and the
accommodating cell placed between them. Simplest plano-convex shape
of the front element allows making inexpensive variation of its
optical characteristics such as dioptric power, asphericity and
toricity for astigmatism correction. Back element of this example
incorporates also haptics and is of more complex shape and is less
variable element of the intraocular lens. Accommodating cell is
secured inside the lens to allow the overall intraocular lens to
demonstrate a conventional shape of a typical non-accommodating
lens.
FIG. 12 illustrates the connection between sensor cell and
accommodating cell. The connecting element is about 6 mm in length
which is adequate to place the sensor cell at the proximity of the
ciliary muscle or more specifically, at the scleral spur for the
interaction. The sensor cell consists of two elements with chambers
connected with the corresponding chambers of the accommodating
cell. These elements of the sensor cell are placed externally and
internally to the ciliary muscle fibers (scleral spur) to create
differential pressure between the chambers of the sensor cell with
muscle contraction or relaxation--pressure at the internal to the
muscle chamber increases and external to the muscle chamber reduces
with the muscle contraction and returns to the original condition
with muscle relaxation.
The shape of the sensor cell of this embodiment consists of two
plates with each chamber situated inside each plate. Each plate has
hard exterior shell and soft interior membrane to respond to the
force from the ciliary muscle and transfer a small amount of
material between corresponding chambers of the sensor cell and
accommodating cell to change the shape of the accommodating element
separating the chambers in the accommodating cell. Only small
amount of material transfer, small fraction of milliliter, is
required to form diffractive surface for near vision from
refractive surface for far vision as shown in this example of the
invention.
FIG. 13 shows the exterior view of the sensor cell in order to
illustrate some specifics of the sensor cell in this example. It
includes two ports each connecting with each chamber of the sensor
cell to allow pressure adjustment between the chambers after
in-vivo installation into the patient and connection with
Diffractive Accommodating Lens. This is in order to adjust for a
proper pressure threshold between the chambers to reliably switch
between the optical states for far and near vision with the ciliary
muscle contraction and relaxation which may depends upon the
patient physiology and sensor cell installation.
FIG. 14 demonstrates aphakic Diffractive Accommodating Lens of this
invention which replaced the natural crystalline lens. The FIG. 12
demonstrates the placement of sensor cell at the location of
anterior tendon that includes scleral spur. Alternatively, it can
be installed at the posterior tendon at the area of ora serrata.
The sensor cell is placed with the exterior chamber being exterior
to the ciliary muscle and the interior chamber to the interior to
the ciliary muscle. The FIG. 12 demonstrates two paths for
connecting element: through the ciliary sulcus posterior to the
iris or iridocorneal angle anterior to the iris. Later will involve
an iridotomy by making a puncture-like opening through the iris
without the removal of iris tissue for the connecting element. The
advantage of iridocorneal angle path is that it is more similar to
the already developed glaucoma surgery technique that involves
glaucoma shunt installation.
FIG. 15 demonstrates Diffractive Accommodating Lens (DAL) of this
invention which compliments a previously installed aphakic
convention IOL which is lacking Presbyopia correction. The DAL is
placed in the commonly acceptable position at the ciliary sulcus in
front of the previously implanted conventional IOL. The sensor cell
and its connection with the DAC is similar to one described in the
FIG. 12.
FIG. 16 demonstrates phakic Diffractive Accommodating Lens (DAL) of
this invention that does not involve a removal of the natural
crystalline lens. The DAL is placed in the iridocorneal angle or by
the iris fixation. The sensor cell and its connection through the
iridocorneal angle with the DAC is similar as one described in the
FIG. 12.
FIG. 17 demonstrates corneal implant Diffractive Accommodating Lens
(DAL) of this invention. The DAL of appropriate shape and thickness
is placed in the cornea and connected to the sensor cell installed
as described in the FIG. 12. The procedure does not require a
penetration inside the eye.
FIG. 18 demonstrates a front view of aphakic Diffractive
Accommodating Lens (DAL) of this invention which replaced the
natural crystalline lens and relies on vitreous pressure or
capsular bag tension change for switching between far and near
vision. These environmental changes caused by ciliary muscle action
affect the DAL directly without a need of sensor cell.
FIG. 19 demonstrates cross-section of the aphakic Diffractive
Accommodating Lens (DAL) of FIG. 16 which replaced the natural
crystalline lens but relies on vitreous pressure or capsular bag
tension change for switching between far and near vision.
FIG. 20, FIG. 21 and FIG. 22 demonstrate optical characteristics of
Diffractive Accommodating Lens of particular optical design in the
eye in terms of longitudinal spherical aberration graphs (LSAs) at
Far image and Near images. Two optical designs for near vision are
shown as the examples.
FIG. 23 and FIG. 24 illustrate diffractive accommodating
spectacles. The DAL spectacles allow to maintain large range of
field for both distance and near vision and also to achieve
automatic accommodation between far and near vision.
FIG. 25 illustrates diffractive accommodating spectacles with the
accommodating cell divided into two zones, one to produce near
focus in stressed condition and another to produce intermediate
focus in stressed condition.
FIG. 26 and FIG. 27 demonstrate Diffractive Accommodating Lens
application to contact lenses. The diffractive accommodating
contact lens can provide accommodation between far and near vision
without a need for the lens precise movement on the eye required
for alternating or segmented contact lens or without compromising
image contrast and overall image quality as in simultaneous vision
multifocal contact lenses.
DETAILED DESCRIPTION
FIG. 1 illustrates a portion of eye anatomy related to the
accommodation process. The ciliary body 100 has three basic
functions: aqueous production and removal, accommodation, and the
formation of vitreous mucopolysaccharide. The ciliary muscle
initiates accommodating process and situates inside the ciliary
body 100. The ciliary muscle contains three types of fibers:
longitudinal 110, radial 120 and circular 130 fibers.
The accommodation function is the primary objective of this
invention and the first order is to describe the ciliary muscle
including their anatomy.
The ciliary body 100 is somewhat triangular in meridional sections
and present circumferentially around the internal surface of the
eye globe. It is narrower nasally (4.5-5.2 mm) than temporally
(5.6-6.3 mm). The anterior margin of the ciliary body 100 is at the
scleral spur 150 is about 1.5 mm posterior to the corneal limbus
160 in the horizontal meridian and 2 mm posterior in the vertical
meridian. Corneal limbas 160 separates sclera 200 and cornea 240.
Ciliary body 100 terminates posteriorly at the ora serrata 170
where the eye retina starts and which is approximately 7.5 to 8 min
posterior to the corneal limbus 160 temporally, 6.5 to 7 mm
nasally, and 7 mm inferiorly and superiorly.
Interiorly and externally, the ciliary body 100 forms a part of the
posterior portion of the anterior chamber angle. The iris 180 is
attached to its anterior and internal surface. Internally, it lies
free and extends internally slightly anterior to the equator of the
crystalline lens 190. Externally, it is adjacent to the sclera 200
with the perichoroidal space between the two. The internal surface
of the ciliary body 100 is adjacent to the vitreous 210. The space
formed by the posterior surface of the iris 180 and the internal
and slightly anterior projection of the anterior-most ciliary
processes 140 is called the ciliary sulcus 220.
The greater part of ciliary muscle is composed of external
longitudinal fibers 110 running anterior-posterior on the inner
aspect of the sclera 200 to insertion into the where muscle stars
are produced referred to as episcleral stars close to ora serrata
170. This muscle is attached to the back of the eye via an elastic
membrane at the suprachoroid (about 8 mm behind the Embus 160) in
the region of the ora serrata 170. Its contraction pulls the
ciliary body 100 forwards and inwards by 0.5 mm during maximum
accommodation. As a result, periphery of the vitreous 210 is also
compressed so that the lens 190 moves forward. The mechanism of
vitreous compression is used in some accommodating IOL design by
Cumming, U.S. Pat. No. 5,476,514 and others and is referenced in
this disclosure as secondary accommodating effect.
The middle radial 120 and internal circular 130 fibers form a
meshwork. The middle radial fibers 220 run obliquely to merge and
attach to the ciliary processes 140. The innermost edge of the
ciliarly muscle contains primarily circular fibers 130. It appears
that circular fibers 130 run in a circle around the ciliary body
100 concentrically with the root of iris 180. Their sphincter like
action contracts the ciliary ring around the lens 190 and thereby
relaxing the anterior and posterior zonules 230. The anterior
portion of the radial and circular fibers project anteriorly and
centrally along a line approximately 45 degrees to the sclera
plane. The ciliary body moves internally by about 0.34 mm and the
equator of the capsule moves internally by about 0.25 mm with the
muscle contraction.
The architecture of all three types of fibers has some general
principles. All 3 are attached anteriorly at the ciliary tendon
(scleral spur 150 and surrounding soft tissue) as Y shaped
extensions with the Y inserting anteriorly into the tendon. The
radial fibers 120 connect to relatively distant parts of the
ciliary tendon and additional anterior fiber attachment to the iris
180. The tension on Scleral Spur effects corneal power so very
slightly, less than 0.1 D and called in this disclosure as 3rd
order accommodating effect. The uniqueness of this invention is to
install a Sensor Cell described below at the area of ciliary tendon
which has easy access. The sensor cell of this invention is used to
transfer the effects of ciliary muscle contraction and relaxation
in a form of pressure change to the accommodating cell of this
invention situated inside the diffractive accommodating lens DAL in
order to switch its states between far and near vision.
The maximum force of contraction of the entire muscle (radial force
extended from ciliary muscle onto the lens 190) increases from
0.85.times.10.sup.-2N at age 15 to about from 1.3.times.10.sup.-2N
at age 45 and then drops to about from 1.1.times.10.sup.-2N at age
55. The entire contraction force reaches the maximum (for
accommodation of about 2.5 D) of 1.2.times.10.sup.-2N (.apprxeq.1.2
g) at age 43 and, importantly, the ciliary muscle action is
maintained throughout the age thus maintaining the effectiveness of
the Sensor Cell.
The aqueous production by ciliary processes 140 together with the
flow of aqueous 250 to the trabecular meshwork 260 and Schleman's
canal 270 are essential for maintaining normal internal eye
pressure and significant body of technology has been developed to
treat the aqueous flow abnormality that lead to glaucoma. Different
surgical techniques and devices (glaucoma shuts, for instance) have
been developed for placement in the area of Schleman's canal 270.
It has appeared that the application of the devices for glaucoma is
practically at the intended placement of the sensor cell at the
scleral spur 150 which is posterior of Schleman's canal 270 by only
1 mm and surgical techniques developed for glaucoma can be applied
to the accommodating system (sensor cell and DAL) of this
invention.
FIG. 2 describes a portion of a prior art ophthalmic device with
diffractive surface 300 with blazed periodic structure 350. It also
explains the optical principle used by accommodating cell of this
invention for switching between far and near vision.
The FIG. 2 includes input light ray 320 refracted at the
diffraction surface blaze and creating diffraction orders indicated
by the directions 320a, 320b, 320c, etc. along which the exited
light can only be channeled. In this case, direction of (+1)-order
diffraction is shown by 320a and (-1)-order diffraction by 320c but
there are infinite orders of diffraction.
FIG. 2 incorporates an explanation of the "geometrical model" of
diffractive lens by including blaze ray 330 as the ray
corresponding to the refraction of the input ray 320 as being
theoretically refracted at the blaze. It is imaginable ray in the
geometrical model of diffractive optic and coinciding with a real
ray in terms of creating the actual image in the direction of the
ray only if the blaze ray coincides with the direction to a
diffraction order. The direction of the blaze ray 330 in the FIG. 2
differs from the direction of O-order diffraction 320b due to the
different refraction angles of the rays at the base curve 340 and
surface relief or blaze structure 350. A particular blaze angle is
created by the selection of the groove height or blaze material
thickness (h).
If the blaze material thickness (h) is zero than the blaze
structure 350 coincides with the base curve 340 and the lens
becomes refractive type. If the blaze material thickness (h)
increases to refract the blaze ray 330 along, say, (-1)-order of
diffraction 320b as shown in the FIG. 2, the lens becomes a
Kinoform with 100% efficiency at (-1)-order diffraction, i.e.
theoretically, 100% of light passing through the lens is directed
to (-1)-order diffraction. In the prefer embodiment of the
diffractive accommodating lens design the state with zero blaze
material thickness is selected to create the optical power for Far
vision (Far power) and non-zero blaze material thickness is to
direct most light along (-1)-order diffraction by the diffractive
accommodating lens for optical power for Near vision (Near
power).
The periodic structure, i.e. radii of the diffraction grooves,
defines the separation between the diffraction orders. This
periodic structure is shown as surface relief structure if blaze
shape in the FIG. 2 where the geometrical model is applied to. The
surface relief structure can take different shape of the
diffraction grooves. The periodic structure may also be in the form
of refractive index modulation structure where the thickness of the
material layer of different refractive index modulates with certain
period to produce diffraction orders.
FIG. 3 shows a simplest form of the Accommodating cell shape as a
rectangular disc of about 4-6 mm diameter D and about 0.10 to 0.3
mm thickness W. The accommodation cell is made of transparent
materials and acts as a lens with optical axis 590. The
accommodating cell diameter acts as the image forming zone of the
lens. In general, the accommodating cell may be curved to take a
desirable shape.
The accommodating cell is situated inside the Diffractive
Accommodating Lens or it may take a shape of the lens by including
necessary curvatures by its external surfaces.
FIG. 4 demonstrates cross-section of the accommodating cell 600
with optical axis 590 in the relaxed state when ciliary muscle is
relaxed. The accommodating cell 600 of this embodiment includes two
chambers 640 and 650 filled with optical fluids (silicone fluids,
for instance) separated by the wall called accommodating element
610 that has the ability to change its surface shape with a
difference in pressure between the chambers 640 and 650. One
chamber 640 filled with optical fluid of matching refractive index
to the accommodating element 610 separating the chambers to make
light passing between the accommodating element separating the
chambers and the optical fluid of the chamber 640 undisturbed by
the surface shape facing this chamber 640. Optical fluid of
non-matching refractive index fills the other chamber 650. As a
result, light refraction only takes place at the surface 560 facing
the chamber 650. Chamber 640 is called optically transparent
chamber (OTC) and chamber 650 is called optically active chamber
(OAC). The FIG. 4 demonstrates that the surface 560 facing the
chamber 650 with non-matching refractive index is smooth and
continuous to form refractive surface type per this preferred
embodiment.
Construction of the accommodating cell in general can be to change
pressure in optically transparent chamber first to drive the change
of the shape of the accommodating element to change the states
between far and near vision or in optically active chamber first or
simultaneously in both chambers as it is explained below with
interaction with dual-chamber Sensor Cell, for instance.
Exterior of chamber 640 is limited by the membrane 620 and the
chamber 650 is by the membrane 630. The accommodating element 610
consists of accommodating sub-elements 680, 690, 700, 710 and so
on. The central sub-element is shown as solid piece situated in
contact with membranes 620 and 630 at the center via corresponding
pins 660 and 670 in order to assist with assembly of the
accommodating cell and also to maintain the accommodating cell
shape integrity for both membranes 620 and 630.
The central sub-element is fairly small; a fraction of millimeter
in diameter and its shape facing the chamber 650 may be either flat
or curved corresponding to the power for far, near or between far
and near. In any case, it is too small to noticeably affect the
overall image quality for eye far or near image. All other
sub-elements are shown with flat surface 560 facing chamber 650.
The sub-elements 690 and 700 are separated by substantially thinner
material portion 570, which is repeated for all other sub-elements
outside the central sub-element 680. These circular material
portions are thin enough to provide bending of the sub-elements in
case of certain level of difference in pressure between the
chambers 640 and 650. Another side of the sub-elements indicated as
580 for sub-element 690 as the same as for others is also thinner
than the rest of each sub-element thickness to assist with each
sub-element bending.
The separation between the sub-elements and membrane 620 is of
width H limiting the maximum bending of all sub-elements. The face
575 of the sub-element 690 facing the neighboring sub-element 700
is narrowed towards its edge between face 575 and face 585 to
prevent bending the sub-element 690 towards chamber 650. The same
construction is applied to all other sub-elements. Thus, bending of
each sub-element is restricted towards the chamber 640 by the
maximum dimension H which is somewhere in the range of 10-20
microns, depending upon the material refractive indices of the
accommodating element and not matching optical fluid and targeted
power difference between far and near vision. Below, the disclosure
offers the specific example of the accommodating element
construction.
All sub-elements have circular shapes around the optical axis 590.
Though the chamber 640 is shown in the cross-section as being
divided by the sub-elements into sub-chambers, all these
sub-chambers are connected with each other by the radial
channels.
FIG. 5 demonstrates a cross-section of the accommodating cell 600
with optical axis 590 in the stressed state when the ciliary muscle
is contracted. As a pressure in the chamber 650 increases because
of some optical fluid is squeezed into it by the accommodation
action, the sub-elements 690, 700, 710 and so on bend at the
thinnest places 720 and so on to create surface relief structure of
the diffractive surface of the accommodating element 610. The
maximum bending is limited to the magnitude H which is the width of
the chamber 640 resulting in the equivalent groove height or blaze
material thickness to produce the Kinoform, i.e. to direct most of
the available light in the direction of (-1)-order diffraction for
near vision.
The accommodating element 610 between the chambers 640 and 650
takes a shape of surface relief of, more specifically, shape of
blazes to form diffractive grooves 740, 750, 760 and so on facing
the chamber 650 filled with non-matching with the material of the
accommodating element refractive index. The diffractive surface
relief heights (blaze material thickness) is restricted by the
geometry H of the accommodating element to create the Kinoform with
the focus for near vision, i.e. 100% of light or most of the
available light is directed to (-1)-order diffraction by the
created diffractive surface relief surface of the accommodating
element 600.
The accommodating element 610 takes shape of blaze of groove height
H if the difference in pressure between the chambers 640 and 650
exceeds certain threshold .DELTA.P. If the difference in pressure
below this threshold .DELTA.P then the light split between far and
near foci similar to a multifocal diffractive lens. Nevertheless,
the benefit of diffractive accommodating lens of this invention is
that light split occurs only in stressed state for near vision
where halo and glare is usually not the issue because of the
presence of significant ambient light required for near vision,
The refractive surface of the accommodating element 610 of FIG. 4
does not manifest diffractive grooves but, for generality, the
refractive surface is defined as the extreme condition of the
surface relief structure of the diffractive surface of the
accommodating element 610 of FIG. 5 with surface relief structure
height H equals zero. Thus, one can say that the refractive surface
of the accommodating element 610 of FIG. 4 has the same periodic
structure as the diffractive surface of the accommodating element
610 of FIG. 5 but their height is zero. In general terms, the
diffractive surface of the accommodating element 610 is called
surface-relief structure which is not limited to a particular
groove shape and the refractive surface 560 of the FIG. 4 is
considered as the special case of the surface-relief structure of
the same period but zero height.
Theoretically, the created Kinoform directs 100% of light to near
focus. Due to the construction restriction, the diffraction
efficiency at (-1)-order is reduced by the surface shape of the
bent material portion 720 and alike between all sub-elements:
.eta..apprxeq..DELTA..times..times.'.DELTA..times..times.
##EQU00004## where .DELTA.r' is reduced from the theoretical period
.DELTA.r of groove equaled to the width of the sub-element due to
so called "shadowing", in this case light passing through 720 and
alike is out of phase for constructive interference at near image
from all sub-elements. The average groove width .DELTA.r is in the
order of 0.1 mm and the width of thin material portion 720 is about
10th of it dimension leading to a theoretical diffractive
efficiency for near vision of about 90%.
The surface relief structure of the Accommodating element 610 is
constructed to produce the same single focus by all its
sub-elements in stressed condition of ocular implants and spectacle
lens in order to maximize the image quality. In case of a spectacle
lens application where eye rotates and viewing through different
portions of the spectacle lens, there is a benefit to divide the
accommodating element into zones with different periods of surface
relief structures of the zones. Under a stressed condition, the
surface relief structure in each zone direct light to different
foci of each zone (-1)-order diffraction. Thus, one zone may be for
near focus and another zone is for intermediate focus and both foci
come into play simultaneously under stressed condition.
FIG. 6 demonstrates cross-section of the accommodating cell 600'
with optical axis 590' in the relaxed state when ciliary muscle is
relaxed. The accommodating cell 600' of this embodiment includes
two chambers 640' and 650' where first chamber 640' is filled with
optical fluid (silicone fluids, for instance) and other chamber
650' is connected to the external medium of the ophthalmic lens.
They are separated by the accommodating element 610' that has the
ability to change its surface shape with a difference in pressure
between the chambers 640' and 650'. The chamber 640' filled with
optical fluid of matching refractive index to the accommodating
element 610' separating the chambers to make light passing between
the accommodating element separating the chambers and the optical
fluid of the chamber 640' undisturbed by the surface shape facing
this chamber 640'. As a result, light refraction only takes place
at the surface 560' facing the chamber 650'. Chamber 640' is
optically transparent chamber (OTC) and chamber 650' is optically
active chamber (OAC). The FIG. 6 demonstrates that the surface 560'
facing the chamber 650' is smooth and continuous to form refractive
surface type per this preferred embodiment.
Exterior of chamber 640' is limited by the membrane 620' and the
chamber 650' is by the membrane 630'. The accommodating element
610' consists of accommodating sub-elements 680', 690', 700', 710'
and so on. The central sub-element is shown as solid piece situated
in contact with membranes 620' and 630' at the center via
corresponding pins 660' and 670' in order to assist with assembly
of the accommodating cell and also to maintain the accommodating
cell shape integrity for both membranes 620' and 630'.
The sub-elements 690' and 700' are separated by substantially
thinner material portion 570', which is repeated for all other
sub-elements outside the central sub-element 680'. These circular
material portions are thin enough to provide bending of the
sub-elements in case of certain level of difference in pressure
between the chambers 640' and 650'. Another side of the
sub-elements indicated as 580' for sub-element 690' as the same as
for others is also thinner than the rest of each sub-element
thickness to assist with each sub-element bending.
The separation between the sub-elements and membrane 630' is of
width H' limiting the maximum bending of all sub-elements. The same
construction is applied to all other sub-elements. Thus, bending of
each sub-element is restricted towards the chamber 650' by the
maximum dimension H' which is somewhere in the range of few microns
to about 20 microns, depending upon the material refractive indices
of the accommodating element and external medium and targeted power
difference between far and near vision.
All sub-elements have circular shapes around the optical axis 590'.
Though the chamber 640' is shown in the cross-section as being
divided by the sub-elements into sub-chambers, all these
sub-chambers are connected with each other by the radial
channels.
FIG. 7 demonstrates a cross-section of the accommodating cell 600'
with optical axis 590' in the stressed state when the ciliary
muscle is contracted. As a pressure in the chamber 650' increases,
the sub-elements 690', 700', 710' and so on bend at the thinnest
places 720' and so on to create surface relief structure of the
diffractive surface of the accommodating element 610'. The maximum
bending is limited to the magnitude H' which is the width of the
chamber 650' resulting in the equivalent groove height or blaze
material thickness to produce the Kinoform, i.e. to direct most of
the available light in the direction of (-1)-order diffraction for
near vision.
The accommodating element 610' between the chambers 640' and 650'
takes a shape of surface relief of, more specifically, shape of
blazes to form diffractive grooves 740', 750', 760' and so on
facing the chamber 650 connected with external medium. The
diffractive surface relief heights (blaze material thickness) is
restricted by the geometry H' of the accommodating cell to create
the Kinoform with the focus for near vision, i.e. 100% of light or
most of the available light is directed to (-1)-order diffraction
by the created diffractive surface relief surface of the
accommodating element 600'.
The surface relief structure of the Accommodating element 610' is
constructed to produce the same single focus by all its
sub-elements in stressed condition of ocular implants and spectacle
lens in order to maximize the image quality. In case of a spectacle
lens application where eye rotates and viewing through different
portions of the spectacle lens, there is a benefit to divide the
accommodating element into zones with different periods of surface
relief structures of the zones. Under a stressed condition, the
surface relief structure in each zone direct light to different
foci of each zone (-1)-order diffraction. Thus, one zone may be for
near focus and another zone is for intermediate focus and both foci
come into play simultaneously under stressed condition.
FIG. 8 demonstrates assembly of the accommodating cell 600 of the
FIG. 4 consisting of three elements: front and back membranes 620
and 630 to form external walls of the chambers filled with optical
fluids and accommodating element 610 forming the wall between the
chambers.
The accommodating element 610 consists of accommodating
sub-elements; one sub-element 690 is pointed to on the FIG. 8. Each
sub-element includes very thin portion 570 between the sub-elements
and thin portion 580 at the opposite side of the sub-element to
assist with its bending. It also may include guides 770 and 780 for
pins 660 and 670 to assist with the assembly and to maintain shape
integrity of the membranes 620 and 640 during accommodating cell
actions.
The elements of the accommodating cell can be made of commonly used
in ocular applications polymers and particularly elastomers
(silicone, acrylic or within the variety of other materials).
The smallest features of the most delicate accommodating element of
the accommodating cell is in microns and can be accurately and
inexpensively reproduced by vacuum casting or injection molding
techniques. In addition, coating can be applied if the elements of
the accommodating cell are too thin to prevent permeability by
optical fluids, for instance, atomic layer of silver coating which
is too thin to interfere with the light transmittance.
FIG. 9 illustrates front view of one of the embodiments of typical
configuration of intraocular lens 410 with optical axis 790 of lens
optic with the optic center O, with the peripheral optical edge
880, haptics or supporting elements 830 and 840 and the addition of
the connecting flexible element 820 attached to the accommodating
cell 600 situated inside the intraocular lens 410 of this
embodiment and shown by its peripheral edge 900. Optical center "O"
is a cross-section of the optical axis 790 with the lens surface.
This definition of the optical center is used throughout this
invention disclosure. The back element of the lens 410 shown by the
peripheral optic edge 880 may include peripheral wedge 890 for
attaching the front element shown by its peripheral edge 910 with
accommodating cell situated between these two elements.
The connecting element 820 is to connect the accommodating cell 600
that changes the optical state between far and near vision with the
sensor cell that interacts with the ciliary muscle to transfer the
force resulted from the ciliary muscle contraction and relaxation
into a difference in pressure between the chambers of the
accommodating cell. The length of the connecting element 820 is
about 6 mm which is adequate to connect sensor cell situated at the
location of the ciliary tendon of the ciliary muscle and
accommodating cell situated inside an intraocular lens.
Upon implantation of lens 410, sensor cell and connecting then by
the connecting element 820, there is a period of stabilization when
the wound heals and capsule bag undergoes possible fibrosis and
shrinkage that may cause uncontrolled pressure on the implant 410
shifting imaging from far to near focus. In order to maintain far
vision during this period, a stabilizing chamber 825 can be part of
the implant construction which tightens the connecting element 820
to prevent a flow of optical fluids in and from chambers of
accommodating cell 600. The stabilizing chamber 825 is filled with
BSS by high enough pressure. The original state of the
accommodating cell 600 set for far vision is then maintained
because the optical fluids are uncompressible.
After the stabilization period when the capsular bag becomes
relaxed, the stabilizing chamber 825 is pierced with Nd:YAG laser
to release BSS and open up the connecting element 820 to allow
optical fluids flow between the accommodating cell 600 and sensor
cell.
This principle to use stabilizing chamber with BSS or any other
physiologically neutral solution to maintain a desirable optical
state by the accommodating implant designed with microfluidic that
can be pierced by a laser beam to restore the implant's dynamic
state, can be applied to any accommodating design that includes
microfluidic action.
FIG. 10 shows the cross-section of the intraocular lens 410 with
optical axis 790 as shown on the FIG. 7. It shows also one of the
haptics 840. The FIG. 10 demonstrates the accommodating cell 600
situated inside the intraocular lens 410 with connecting element
820 attached to it at one end 930 and the other end 870 of the
connecting element is attached to the opposite edge of the
intraocular lens optic for its temporary fixation during lens
implantation inside the eye. This end 870 is separated from the
intraocular lens inside the eye for connection to the sensor
cell.
The FIG. 8 demonstrates the stabilizing element 825 blocking the
connecting element 820 to prevent optical fluids to flow in and out
of the accommodating cell 600 in order to maintain far vision
during stabilizing period.
The lens 410 consists of front elements 800 with the front surface
850 and back element 810 with the back surface 860. The front
element 800 may be attached to the back element 810 via the wedge
mechanism 920 as an inexpensive assembly of the whole lens 410.
FIG. 11 illustrates assembly of the intraocular lens 410 shown on
the FIGS. 9 and 10. The intraocular lens of this particular
embodiment consists of three elements: front element 800 which can
be attached to the back element 810 at the front wedge 920 and the
accommodating cell 600 placed between them. Simplest plano-convex
shape of the front element enables making an inexpensive variation
of its optical characteristics, such as a variety of dioptric
powers, asphericity and toricity for astigmatism correction, by
shaping the front surface 850. Back element 810 of this embodiment
incorporates also haptics 830 and 840 and is of a more complex
shape and is less variable element of the intraocular lens
manufacturing. Accommodating cell 600 is situated in the hollow at
the front of the back element 810 in contact with surface 950 and
is secured inside the lens 410 by front element 800 to allow the
overall intraocular lens 410 to take a conventional shape of a
typical non-accommodating lens and, therefore, to utilize
convention implantation techniques.
The connecting element 820 is permanently attached to the
accommodating cell at 930 and secured to the lens 410 at the
opposite end 870 for the lens 410 implantation and then the end 870
is attached to the sensor cell.
FIG. 12 illustrates the connection between sensor cell 605 and
accommodating cell 600. The connecting element 820 is about 6 mm in
length which is adequate to place the sensor cell at the proximity
of the ciliary muscle for the interaction and accommodating cell to
be situated inside the Diffractive Accommodating Lens of this
invention.
A dual chamber sensor cell 605 per this example consists of two
plates 360 and 370 with chambers 980 or 1010 inside of each plate
connected with the corresponding chambers 640 or 650 of the
accommodating cell 600. The plates 360 and 370 of the sensor cell
605 are placed externally and internally to the ciliary muscle
fibers with the ciliary tendon situated in between to create a
differential pressure between the chambers 980 and 1010 of the
sensor cell 605 with muscle contraction and relaxation. Pressure at
the internal to the muscle chamber 1010 in the plate 370 increases
and external to the muscle chamber 980 at the plate 360 reduces
with the muscle contraction when the ciliary muscle moves inward
and the pressure in the chambers 360 and 370 returns back to the
initial state with ciliary muscle relaxation.
Each plate 360 or 370 has hard exterior shell 960 or 990 and soft
interior membrane 970 or 1000 to respond to the force exerted by
the ciliary muscle and then to transfer the difference in pressure
between the sensor cell chambers 980 and 1010 to the difference in
pressure between the accommodating cell chambers 640 and 650 via
the channels 1020 and 1030 of the connecting element 820.
The corresponding change in pressure between the chambers 640 and
650 of the accommodating cell 600 switches the optical states of
the eye between far vision with ciliary muscle relaxation and near
vision with ciliary muscle contraction. The pressure threshold is
set at the sensor cell 605 between these two corresponding levels
of pressure for a reliable change in states of the accommodating
cell between far and near vision.
FIG. 13 illustrates some specifies of the dual chamber sensor cell
605 exterior views facing outside the eye, i.e. front view of the
plate 360 with the chamber 980 inside. The other chamber 1010 is in
the internal plate 370. The exterior of the sensor cell 605 is
shown with two ports 1040 and 1050 each connected to each chamber
980 or 1010 to allow in-vivo pressure adjustment between the
chambers of the sensor cell after the installation of the sensor
cell, Diffractive Accommodating Lens and their connecting after the
surgery. This is in order to adjust for a proper pressure threshold
between the chambers 640 and 650 of the accommodating cell to
reliably switching between the optical states of far and near
vision with contraction and relaxation of the ciliary muscle of the
patient. The adjustment might be beneficial due to individual
variation in ciliary muscle action and sensor cell positions.
The sensor cell can be of different shape and construction and have
one chamber with the fluid to interact with the ciliary muscle
contraction to transfer the resulted force to the accommodating
cell to switch from far to near vision.
FIG. 14 demonstrates aphakic Diffractive Accommodating Lens 410 of
this invention which replaces the natural crystalline lens and
consisting of optic 400 and haptics 420. The DAL 410 is shown as
being placed inside the capsular bag 290. The FIG. 14 demonstrates
the placement of the sensor cell with external plate 360 and
internal plate 370 around the anterior tendon of the ciliary muscle
that includes scleral spur 370. The sensor cell is placed with the
exterior plate 360 with its the exterior chamber being exterior to
the ciliary muscle 110, 120, 130 and the interior plate 370 with
its interior chamber to the interior to the ciliary muscle 110,
120, 130. The FIG. 14 demonstrates two paths of the connecting
element 430 between the sensor cell and accommodating cell: through
the ciliary sulcus 220 posterior to the iris 180 or iridocorneal
angle 280 anterior of the iris 180, path 440. Later will involve an
iridotomy by making a puncture-like opening through the iris
without the removal of iris tissue for the connecting element to go
through the iris 180. The advantage of iridocorneal angle path 440
is that it is more similar to the already developed glaucoma
surgery technique that involves a glaucoma shunt installation.
FIG. 15 demonstrates Diffractive Accommodating Lens (DAL) 460 of
this invention which compliments a previously installed aphakic
convention IOL 450. The DAL 460 includes haptics 470 placed in the
commonly used position at the ciliary sulcus 220 in front of the
previously implanted conventional IOL 450. The sensor cell with
plates 360 and 370 is similar to those described in the FIG. 14.
The connection 430 of the sensor cell and DAC 460 is also may have
two paths, one through the ciliary sulcus 220 and another through
iridocorneal angle 280 to the DAL 460 and are similar to those
described in the FIG. 14.
FIG. 16 demonstrates phakic Diffractive Accommodating Lens (DAL)
500 of this invention that does not involved a removal of a natural
crystalline lens 190. The DAL 500 is shown as being placed with its
haptics 510 in the iridocorneal angle 280 but the phakic DAL can
also be iris fixated, i.e. the lens haptics are attached to the
iris 180, or phakic DAC can be placed behind the iris 180 and in
front of the crystalline lens 190. The sensor cell with plates 360
and 370 is similar to those described in the FIG. 14. The sensor
cell and its connection element 520 through the iridocorneal angle
280 with the DAC 500 is similar as one described in the FIG.
14.
FIG. 17 demonstrates corneal implant Diffractive Accommodating Lens
(DAL) 530 of this invention which is placed in the cornea 240. The
DAL 530 of appropriate shape to match the corneal shape and
thickness is placed in the cornea 240 and connected to the sensor
cell with plates 360 and 370 is similar to those described in the
FIG. 14. The DAL 530 is connected with sensor cell with connection
element 540 that goes over the cornea 240. The procedure does not
require a penetration inside the eye.
FIG. 18 illustrates another option of the aphakic diffractive
accommodating lens 1100 operation that changes its optical states
between far and near vision by direct effect of the vitreous
pressure or capsular bag tension. As a secondary accommodating
effect, ciliary muscle contraction changes choroid tension thus
increases vitreous pressure causing crystalline lens-zonule complex
to move forward. The effect is also observed with the crystalline
lens replacement by aphakic IOL which can move by about 0.1-0.2 mm
either forward or even in some instances, backward. Due to
diffractive design of the diffractive accommodating lens, a
direction of movement is irrelevant as long as there is a change in
vitreous pressure and the pressure threshold of the accommodating
cell is set within the range of the vitreous pressure
variation.
The DAL 1100 consists of front element 1110, back element 1140 and
accommodating cell 1160 between them. Front element 1110
incorporates supporting members or haptics 1120 and 1130 to secure
lens 1100 position inside the eye. Back element 1140 is attached to
the front element 1110 via sub-chambers 1190, 1200, 1210 and 1220
(could be a different sub-chamber design) connected with the
accommodating cell 1160 chamber with optical fluid of non-matching
refractive index, optically active chamber, with accommodating
element material to allow fluid to travel between them. The other
optically transparent chamber with matching refractive index is
connected with sub-chamber 1180 supported by a flexible membrane to
allow its volume to change if the optical fluid is squeezed out
from the connecting chamber of the accommodating cell by the
pressure from the sub-elements 1190 etc., due to external forces
such from the vitreous, for instance. The pressure might be
required to be adjusted for relaxed state post-operatively after
the healing and lens stabilization inside the capsular bag. This
might be performed through a chamber port using a needle.
A DAL may only include optically transparent chamber and function
of optically active chamber is taken by the aqueous humour. In this
case accommodating element is facing the aqueous humour one side
and optically transparent chamber on another.
FIG. 19 demonstrates a cross-section of the diffractive
accommodating lens 1100 of the FIG. 18. The lens consists of front
element 1110 that includes haptic with one haptic 1130 shown on the
FIG. 19. Back element 1140 is held onto the front element 1110 by
the wedge structure 1170 and attached to the front element 1110 via
sub-chambers 1190 and 1200. These sub-chambers can be of different
number and shape.
Vitreous pressure shown by 1239 is exerted on the back element 1140
with variable magnitudes depending on the ciliary muscle
contraction and relaxation as well as the lens 1100 fixation inside
the eye. This in turn, changes the pressure on the sub-elements
1190, 1200 and others, transferring small amount of the optical
fluid into the accommodating cell 1160 chamber with non-matching
refractive index. This in turn changes the shape of the surface
relief of the accommodating element facing non-matching refractive
index chamber by transferring a small amount of optical fluid from
the matching refractive index chamber into the corresponding
sub-chamber 1180 by flexing its membrane. Sub-chamber 1180 is shown
as a ring structure around the accommodating cell external edge but
it can be of a different shape and location with maintaining the
principle of operation of changing accommodating element surface
shape from refractive to diffractive or between orders of
diffraction to redirecting light between far and near foci.
The ophthalmic lens described by the FIG. 19 can be substantially
simplified with the use of the accommodating cell 600' described by
FIGS. 6 and 7. The sub-chambers 1190 and so on are replaced by
sub-chambers connected to the optically transparent chamber (OTC)
filled with optical fluid of matching refractive index with
accommodating element and the optically active chamber is connected
to the exterior medium such as aqueous humour. The amount of fluid
transfer from sub-chambers to OTC may control the bending of the
accommodating elements that creates surface relief structure. No
need for sub-chambers 1180 and so on connected with the optically
active chamber of the accommodating cell.
Upon implantation the lens 1100 into the capsular bag, there is a
few months period when the capsular bag may shrink and change
tension on the lens 1100 impacting its relaxed state for far
vision. One option to handle this period is to include so called,
stabilizing sub-chamber 1185 shown as narrow circular shape in this
case separating the front 1110 and back 1140 elements and filled
with BSS, for instance. The stabilizing sub-chamber 1185 maintains
stability of the lens 1100 during this initial post-operative
period by preventing a dynamic change in the optical state until
the ocular condition becomes stable. Patient maintains normal Far
vision equivalent to any conventional monofocal lens during this
period. After the ocular condition is stabilized, the stabilizing
sub-chamber 1185 is punctured with a Nd:YAG laser beam, for
instance, allowing BSS to be removed into aqueous thus reversing
the lens 1100 to the dynamic condition to enabling it to change
between relaxed state for Far vision and stressed states for Near
vision with absence and presence of accommodating force. Only a
small amount of optical fluid, small fraction of milliliter, is
transferred in and from the corresponding chambers that involved in
changing the shape of the accommodating surface that separates both
chambers of the accommodating cell 1160 and switches between far
and near vision. The process does not rely on a lens forward
movement as with other accommodating IOLs but only on a pressure
change required for material transfer in the chambers but only
requires that back element 1140 and front element 1110 are squeezed
together by about 10-20 microns by the action of ciliary muscle,
choroid and vitreous. The lens 1100 itself may move forward or
backward during this process which is likely not to exceed a small
fraction of millimeter.
The sub-chambers 1200 the diffractive accommodating lens may have
transferred to the sensor cell installed to interact with the
ciliary muscle directly. In this case, the sensor cell has only one
chamber with the fluid and some function of the other chamber
described above is taken by the sub-chamber 1180.
If the diffraction accommodating lens design relies on changes of
the capsular bag tension, then the construction of the
accommodating cell must be different from 600 or 1160 above by
providing near vision at the resting state of the capsular bag and
far vision at the increased tension of the capsular bag.
The diffractive accommodating lens can be also applied to dual-lens
system, U.S. Pat. No. 7,452,378 that relies on the capsular bag
action to change optical states between far and near vision. In
this case, the accommodating element is to provide far vision in
stressed state and near vision in relaxed state to follow the
capsular bag actions which is accomplished by either to have
diffractive surface with (-1)-order diffraction at relaxed state
(near vision) and refractive optic in stressed state (far vision),
or refractive optic in the relaxed state (near vision) and
diffractive surface with (+1)-order diffraction in stressed state
(far vision).
FIG. 20 provides a Longitudinal Spherical Aberration at Far image
formed by the Diffractive Accommodating Lenses DAL 1 and DAL 2 per
the specifications listed in the Tables 1 and 2 as being examples
of the invention.
TABLE-US-00001 TABLE 1 Eye model specifications where Diffractive
Accommodating Lenses 1 and 2 were analyzed. Optical Characteristics
Cornea: Dimension in mm; refractive index Anterior surface radius
7.8 Refractive index 1.377 Conic constant (asphericity Q) Nominal Q
= -0.26 Posterior surface radius (mm) 6.5 Central thickness (mm)
0.55 Aperture stop or pupil position from 3.55 posterior corneal
surface (mm) Aqueous refractive index 1.3374 Vitreous refractive
index 1.336
TABLE-US-00002 TABLE 2 Overall Specifications of Diffractive
Accommodating Lens 1 and 2. Optical Characteristics Dimension in
mm; refractive index Power (D) 21.0 Front element front surface
vertex radius 17.55; bi-sign aspheric(*) material Acrylic, 1.489
thickness 0.30 back surface radius flat Accommodating Cell
plano-parallel plate Acrylic, 1.489; 0.1 mm thick Chamber A-E
Optical fluid, 1.433 Switchable Element (SE) Silicone, 1.433; 0.1
mm thick Chamber A-I Optical fluid, 1.403; 0.05 mm thick
plano-parallel plate Acrylic, 1.489; 0.1 mm thick Back element
front surface radius flat material Acrylic, 1.489 thickness 0.60
back surface radius -8.01 (*)Bi-sign aspheric has been disclosed by
Portney in U.S. patent application No.: 12/415,742. Aspheric
coefficients of the front surface referenced to in the Table 2 are:
-0.0015 at r.sup.4, 0.000172 at r.sup.6, 0.00000446 at r.sup.8 and
0.000006 at r.sup.10.
The LSAs of Far images of DAL 1 and DAL 2 are the same because the
refractive specifications of both lenses are the same. The LSA
demonstrates positive spherical aberration for up to about 1 mm
from the lens center and negative spherical aberration outside 1 mm
distance which is the characteristic of bi-sign asphericity.
The surface for far vision can be also made with a power variation
to increase depth of focus at far. For instance, to have higher
power at the center and then progressively reduced power to create
negative power slop known as increasing depth of focus. The power
progressive may be up to 1 D with only marginal impact on image
quality but to reduce sensitivity to residual refractive error.
FIG. 21 and FIG. 22 provide Longitudinal Spherical Aberrations at
Near images by the Diffractive Accommodating Lenses DAL 1 and DAL 2
produced at (-1)-order diffraction per the specifications of Eye
model, Diffractive Accommodating Lenses 1 and 2 provided in the
Tables 1 and 2. The surface of the accommodating element facing OAC
acting as imaging zone that switches between far and near vision is
placed within about 4 mm diameter as shown on the Table 3 below.
The LSA graphs show near LSA within this diameter and portion of
far LSA outside 4 mm diameter as the LSA graphs is shown for 5 mm
diameter on the FIGS. 19 and 20 and thus capturing some of far LSA
close to 5 mm diameter (2.5 mm distance from the lens optical
center),
DAL 1 includes only small amount of spherical aberration in the
(-1) order diffraction to produce close to spherical wavefront in
creating near retinal image at 36 cm of near viewing distance. DAL
2 includes a significant amount of spherical aberration in the
(-1)-order diffraction to create retinal image from a near object
placed not only around 36 cm viewing distance as in DAL 1 but at up
to about 27 cm of near viewing distance, i.e. to offer the
increased depth of focus at near of about 1 D. The increase in
depth of focus at near is demonstrated by the corresponding LSA
shape on the FIG. 20 which starts at more near focus at the lens
center and gradually shifts farther away to create a negative slope
of the power graph. The extension of the range of vision towards
closer near is beneficial as there is a natural tendency to bring a
near material closer to the eyes to observe finer details. The
increased depth of focus of about 1 D at near may be shifted to
intermediate vision by providing a range of vision from about 50 cm
at intermediate to 36 cm at near. This is to expend the
effectiveness of the diffractive accommodating lens from far and
near to include intermediate vision.
Specifications of the diffractive surfaces of the Accommodating
cells with small amount of spherical aberration for near image (DAL
1) and large amount of spherical aberration to extend depth of
focus at image by (-1)-order diffraction (DAL 2) are provided in
the Table 3.
TABLE-US-00003 TABLE 3 Specification of the near diffractive state
of (-1)-order diffraction of the Accommodating cells of the
Diffractive Accommodating Lens DAL 1 and DAL 2. Per materials
specified of Table 2 the diffractive H = 0.0183 mm to create
Kinoform in grooves heights (blaze material thickness) are constant
compressed state of the Accommodating Cell Phase coefficients
(radians) .alpha..sub.i of the Phase Function .PHI..sub.-1(r.sub.i)
per Eq. 3 r r.sup.2 r.sup.4 r.sup.6 DAL 1 (small spherical
aberration) 0.231 20.968 1.116 -0.23 DAL 2 (large spherical
aberration) 0.168 31.867 -4.215 0.340 Groove radii (mm) 1 2 3 4 5 6
7 8 9 10 11 12 13 DAL 1 0.538 0.738 0.925 1.065 1.187 1.298 1.400
1.496 1.586 1.673 1.758 1.- 841 1.923 DAL 2 0.447 0.642 0.799 0.937
1.065 1.187 1.305 1.422 1.537 1.653 1.768 1.- 881 1.981
The groove height H is to provide 100% diffraction efficiency for
(-1)-order diffraction or at least to direct most of the available
light to near focus, i.e. the Diffraction Accommodating Lens in the
corresponding diffractive state becomes the Kinoform. If groove
height is only a fraction of H because a difference in pressure
between the chambers is below the threshold, the DAL becomes a
multifocal diffractive lens that split light between Far and Near
foci. The corresponding vision is only for near because of the
presence of some accommodating force which only occurs for near
vision. It takes only to achieve 40% of H for a grooves height
(maximum height for Kinoform) in order to direct 30% of light to
Near focus and achieve sufficient near vision. In case of the
example on the table 3, it takes 7 microns or more of grooves
height to direct 30% or more of total light to Near focus.
Diffractive Accommodating Lens DAL 1 changes between two distinct
foci of Far image demonstrated by far LSA in the FIG. 18 and Near
image demonstrated by near LSA in the FIG. 21. Depth of focus or
progressive foci feature at near can be increased as shown in DAL 2
by modification of the phase coefficients for (-1) order
diffraction to include spherical aberration that spreads light
along the optical axis at the near image either to improve near
close up or improve intermediate vision capability in addition to
near. This extension of depth of focus at (-1)-order diffraction is
accomplished independently of the Far image LSA.
Another option to introduce multiple foci (near and intermediate)
in stressed condition is to use multi-zone option, i.e. to divide
the accommodating element into zones that under stress condition
produce surface relief of different periodic structure resulting in
different foci of (-1)-order diffraction of each zone. This way one
zone, central for instance, may manifest intermediate focus and
peripheral annulus zone to provide near foci or vice versa. Similar
multi-zonal option can be also applied to the switchable
diffractive surface that is based on the refractive index change
where zones have different refractive index amplitudes.
The near focus of DAL 1 and DAL2 can be in the range that
corresponds to intermediate vision and for generality the meaning
of near focus referenced in this invention also includes
intermediate focus, i.e. any focus produced by the accommodating
cell in stressed state over the far focus produced in the relaxed
state.
The result of the depth of focus increase at (-1)-order of
diffraction for DAL 2 involves the change in the diffraction
grooves shape which is illustrated by the difference in groove
radii between DAL 1 and DAL2. The grooves radii of DAL 1 with small
amount of spherical aberration is practically equivalent the
grooves radii defined by the paraxial approximation of the Equation
1. Both DAL 1 and 2 include 13 grooves within about 4 mm diameter
with central two grooves radii DAL 2 being substantially smaller
the corresponding grooves in DAL 1 and also by the radius of a more
peripheral groove of DAL 2 reaching a similar magnitude as the
radius of the same groove order in DAL1, on 11th groove in the
Table 3 of this example. Substantially smaller in general means
about 10% of more smaller. Substantially similar usually means
within .+-.10%. The radii of further grooves of DAL 2 then may
exceed the radii of the corresponding grooves of DAL 1. This
comparison between the grooves of any diffractive lenses that
produces small amount of spherical wavefront (DAL 1) with the radii
defined by the paraxial form of the Equation 1 and wavefront with
extended spherical aberration that increased depth of focus (DAL 2)
is applied to the same orders of diffraction and the same image
positions defined by the diffraction order focal length.
In case of an annular zone with progressive foci feature, the radii
of central grooves reference to the grooves starting at the
internal side of the annular zone, i.e. a reference to "central
grooves" includes central grooves of a zone that includes optical
center of the lens or an annular zone.
Similar phase coefficients modification to enhance depth of focus
at near can be applied to monofocal diffractive non-accommodating
lens, multifocal diffractive optics where light is split between
far and near foci and near image is formed, for example, by
(-1)-order diffraction and switchable diffractive surface that is
based on the change in the refractive index modulation. Appropriate
phase coefficients can be applied to the multifocal diffractive
optic, for instance, to lead to similar diffractive grooves shape
change from the one producing spherical wavefront to result in the
increase in depth of focus for (-1)-order diffraction. The result
will be the same correlation between the diffractive grooves as
those in comparing DAL 1 as defined by the paraxial form of the
Equation 1 and DAL 2 in the Table 3.
The difference between a DAL and corresponding multifocal optic
would be grooves height or blaze material thickness in case of
blaze grooves: the grooves heights in multifocal optic is to split
light between far and near images and in DAL is to direct most of
the available light to the diffractive focus.
Spherical aberration of Far image can also be expended to enhance
depth of focus at far towards intermediate independently of the
near image depth of focus extension. This can be accomplished by
modifying at least one of the refractive surfaces of the
Diffractive Accommodating Lens including the refractive surface of
the Accommodating Cell formed in the state of Far vision shown in
this particular embodiment.
FIG. 23 and FIG. 24 illustrate diffractive accommodating lens for
spectacles. Almost universally, the series of front surface base
curves to cover the entire spectacles prescription range is used.
This system reduces lens inventory and eliminates the need for a
different base curve for every possible prescription. Sets of
semi-finished blanks, with front curves varying in steps, are
stocked in local optical laboratories, and charts or computer
programs show laboratory personnel which blank should be used for
each prescription. The system was developed from the ability to
have spectacle lens bending (combination of front and back surface
curvatures) that limits power error and oblique astigmatism error
with eye rotation and viewing through different area of the
spectacle lens. Eye rotation is usually up to 30 degrees or even 40
degrees from the optical axis on each side of the spectacle lens
optical center.
The disclosed Diffractive Accommodating Lens for spectacles 1300 is
built around the same system of front base curves by adding
Accommodating Cell described above and shaped it similarly to the
base surface onto the front base surface of the single vision
spectacle lens, 1310 and 1320. This is one of the embodiments but
the design is not limited to this particular description as the
accommodating cell may be either add-on or as the insert. The back
surface of the lens may include spherical and tone surface
equivalent to single focus prescription of the same wearer of the
glasses.
The Accommodating Cell of the Diffractive Accommodating Lens may
include two chambers OTC and OAC or only one chamber OTC if the
surface relief structure of the Accommodating Element faces the air
which acts as OAC. In later case it is desirable for the surface
relief structure to face the base surface for its protection. The
front membrane of the Accommodating Cell facing the exterior of the
lens can be made thick enough to maintain Accommodating Cell
integrity during lens cleaning.
The chambers of the Accommodating Element are connected to the
control mechanism 1340 consisting of two chambers each connected to
the corresponding chamber of the Accommodating Cell and separated
by the moving separator connected to the nub 1350. The nub 1350 can
be moved be the wearer from one end to another to push the optical
fluid in the control mechanism 1340 in and out of the corresponding
Accommodating Cell chambers in order to change Accommodating Cell
states between far and near vision. The mechanism arrangement can
be more conspicuous by placing it in the skull temple 1370.
The near vision state of the accommodating cell is demonstrated on
the FIG. 24 by the non zero height diffractive grooves 1410 and
1420 centered at the near vision centers at both spectacle lenses
placed below the corresponding far vision centered 1415 and 1425
which practically coincide with optical centers of the
corresponding spectacles lenses. The nub 1350 is shown at its left
position for far vision in the FIG. 23 and right position for near
vision in the FIG. 24. The Accommodating cell of the lens at the
other side of the spectacles 1310 is also connected to the control
mechanism 1340 via line 1360 be connecting element as a tube
passing through the bridge 1380 and also the nose pad 1390
depending upon the frame construction. This is to allow switching
between far and near vision in both spectacle lenses
simultaneously.
The diffractive grooves 1400 are optically designed to minimize
power and oblique astigmatism errors for near vision with eye
rotation within comfortable field of about 15-30 degrees range in
different directions from the near vision optical center located at
the lower portion of each spectacle lent and closer to the middle
of spectacles than the optical center of each lens that considers
with far vision center.
The surface relief structure of the Accommodating Cell may have
multi-order diffraction where the phase period between the grooves
is scaled up by the multiple factors, for instance by factor of
4-6. The benefit of the multi-order diffraction is the reduced
chromatic aberration which is particularly importance for spectacle
lenses where the control of transverse chromatic aberration raised
with eye rotation is important.
The major issue with present day glasses for Presbyopia is the
inability to see things that are close or intermediate, but
straight ahead. The DAL for spectacles allows addressing this issue
by expending the area for far and near vision by switching between
different states. The lens also allows addressing intermediate
vision in three options:
(A) Trifocal arrangement to use +1-order diffraction for far,
zero-order for intermediate and (-1) order for near or
superposition of two periodicities of different add powers. There
is the ability for precise control of optical fluid in and out of
the accommodating cell chamber to switch between not only two but
three diffraction orders. For instance, by removing the precise
amount of fluid form the OAC, the accommodating element is bent in
opposite direction from the previously explained (-1)-order
diffraction to produce +1-order diffraction, and also by injecting
the precise amount of fluid into the OAC to produce (-1) order
diffraction. In this case, the relaxed state would be for
intermediate vision. (B) Another option is to include the near
vision with progressive diffractive design as explained by the FIG.
22. In this case, the intermediate power between far and near range
covers the center of the lens to allow the wearer to look straight
ahead for intermediate, computer screen, for instance. (C) The
third option is to divide the accommodating element into zones of
different periodic structures thus the separations between
diffraction orders are different between the zones. It means they
produce different foci for (-1)-order diffraction as explained by
the specifications to the FIG. 5 or 7. Near zone, i.e. zone that
produces shorter focal length by its (-1)-order diffraction for
near and it is placed at the center of near vision below the
optical center of the spectacle lens that concedes with the center
for far vision. Peripheral zone, i.e. zone that produces longer
focal length by (-1)-order diffraction for intermediate includes
optical center of the spectacle lens to allow wearer to look
straight ahead onto intermediate object such as a computer screen,
for instance. Both zones may take large areas of the spectacle lens
to allow for a comfortable field because they replace far power
area by switching the accommodating element and not just
complimenting the area of far vision as in conventional bifocals,
trifocals and progressive glasses.
FIG. 25 illustrates a preferred embodiment of spectacle lens to
provide far vision in one optical state and another state is a
combination of (B) and (C) options described under the FIGS. 23 and
24 above where the accommodating cell is divided into two zones in
the activated optical state, central zone around 1410' and 1420' to
produce near focus in stressed condition and peripheral around
optical centers 1415' and 1425' of the spectacle lenses to produce
intermediate focus. The corresponding multizone structure of
different periodic structures of the diffractive grooves creates
different foci for (-1)-order diffraction between different zones.
The imaginable lines separating the zones are shown as 1430 and
1435 to illustrate the location of near focus zone and intermediate
focus zone.
A change in pressure to switch between different states of surface
relief periodic structure heights can be accomplished only
mechanically with optical fluid transfer to and out of the optical
transparent changer but also electronically by changing magnetic or
electrical states of the accommodating element and membranes. For
instance, changing the magnetic states of the accommodating element
and membrane forming the chamber into opposite or the same
polarities would increase or reduce pressure between the
accommodating element and the membrane forcing the accommodating
element to change the surface relief structure height and,
therefore, redirecting light from one diffractive order to another
(including zero order created by refractive surface).
The intermediate annular zone includes progressive foci change as
shown under FIG. 22 in reference to DAL 2 but for the annular zone.
This progressive change in foci is from intermediate at 1415' and
1425' with foci reduction towards lines 1430 and 1436 to the level
of near focus is in order to have a smooth foci transition from the
peripheral intermediate vision zone and central near vision zone of
the accommodating cell thus avoiding an image jump common with
abrupt foci change when the eye moves through this abrupt focus
change. The peripheral zones of the intermediate focus of the
accommodating cells of left and right spectacles lenses includes
corresponding optical centers 1415' and 1425' to allow the wearer
to look onto intermediate object straight ahead without tilting the
head or training eyes to look through a specific area of the
spectacle lens.
Multizone structure of different periodic structures of the
diffractive grooves that results in different foci for (-1)-order
diffraction between different zones can be further expanded to be
used as indicator of the optical state of the spectacles.
Additional zone is placed at the right periphery of right spectacle
lens and left periphery of the left spectacle lens. The surface
relief periodic structure for (-1)-order diffraction of this third
zone has substantially smaller periods than near zone thus
producing focus that is out of focus from retinal imaging.
Therefore, the corresponding zone does not produce imaging for
object at any distance, it effectively reduces the field of the
spectacle lens in horizontal plane. This can be used as an
indicator to the wearer in watt state his or her spectacles are--in
relaxed state for far vision or stressed state for near vision.
The principle of multizone structure that includes different zones
of periodic structure of the diffractive grooves producing
different foci for (-1)-order diffraction at different zones
manifested in stressed state may be applied to the spectacle lens
with refractive index modulation as the improvement over the
switchable lens described by Li and his colleagues and referenced
to above. In this case the spectacle lens includes zones of
different refractive index amplitudes. For instance, the spectacle
lens produce far vision with refractive surface and near vision
with non-zero diffractive order created by refractive index
modulation from the original refractive surface and the diffractive
surface is divided into at least two zones of different periodic
structure to produce different focus positions for the same
non-zero diffractive order simultaneously such as near and
intermediate foci. The improvement may also include a foci
transition between intermediate vision zone and near vision zone to
avoid image jump.
System for automated switching between far and near vision can be
also added to the Diffractive Accommodating Lens by including gaze
distance detection. Gaze distance detection includes a combination
of emitter-sensors for infrared radiation placed at the spectacle
lens or spectacles frame. It is based on the measurement of
convergence angle between line of sights of right and left eyes
from which the object distance is calculated. The light of sights
are measures by detecting the reflection off the corneas or pupil
tracking or by more accurate methods such as a comparison of the
reflection from front corneal surface with either the pupil
position or 4th Purkinje image (reflection from back surface of the
eye's lens). One of the emitter-sensors is shown as 1330 and the
FIGS. 23 and 24 to demonstrate one of three emitter-sensors per
each spectacle right and left sides to apply triangulation.
The signal from the sensors is passed to the microprocessor placed
in the skull temple 1370 to calculate the gaze distance to the
viewing object. As the distance lies within a near range, the
corresponding signal is sent to the electronic control mechanism
placed in place of 1340. It can be a micro solenoid acting as
toddle switch to move armature that pushes the optical fluid
similar to the described above mechanical control mechanism 1340.
The manual override might be still included.
FIG. 26 and FIG. 27 demonstrate Diffractive Accommodating Lens
application to contact lenses. The design utilizes a principle of
bifocal segmented lens where the lens rides up pushed by the lower
lid when the wearer looks down to look through the lower near
segment of the lens. The lens rides down by its gravity when the
wearer looks up to look through the distance segment of the lens.
The key point is that the lower lid applies pressure to the lens to
ride it up which is used to control switching between far and near
vision of the Diffractive Accommodating Lens 1450.
The lens 1450 is facing by front surface 1470 in the FIG. 23 and
the Accommodating Cell 1500 is represented by the diffractive
grooves 1460. Per the FIG. 26, the chamber 1480 filled with optical
fluid is pressured by the lower lid when the wearer looks down.
Similar to a segmented lens, the lens 1450 utilized the weighted
bevel at the bottom of the lens, 1510 with the chamber 1480 inside
it to minimize the lens rotation. The back surface 1490 shape can
be maintained similar to one in a typical bifocal segmented
lens.
The contact lens can be also constructed with only optically
transparent chamber and the air at the front surface of the lens or
tear layer at the back surface to function as the optically active
chamber. In this case, the front or back surface of the lens
changes between refractive shape for far vision and diffractive
shape of (-1)-order diffraction for near vision. This simplified
construction allows to make the lens as thin as the corresponding
segmented single focus lens.
When the wearer looks down, the lens 1450 maintains its position
but the pressure from the lower lid transfers small amount of
optical fluid to the Optically Transparent Chamber of the
Accommodating Cell 1500 of the lens switching it from far to near
vision. As the wearer looks up, the pressure on the chamber 1480 is
released and the Accommodating Cell 1500 takes the relaxed state
for far vision. The benefit over the segmented lens is that there
is no need to precise lens fitting for proper riding up and down as
the most of lens area is switched between far and near vision thus
simplifying the fitting and reducing a likelihood that a wrong
segment interferes with the vision.
Although there has been hereinabove described a specific switchable
diffractive accommodating lens and method in accordance with the
present invention for the purpose of illustrating the manner in
which the invention may be used to advantage, it should be
appreciated that the invention is not limited thereto. That is, the
present invention may suitably comprise, consist of, or consist
essentially of the recited elements. Further, the invention
illustratively disclosed herein suitably may be practiced in the
absence of any element which is not specifically disclosed herein.
Accordingly, any and all modifications, variations or equivalent
arrangements which may occur to those skilled in the art, should be
considered to be within the scope of the present invention as
defined in the appended claims.
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